Butt joining of steel bars and connection assembly therefor

ABSTRACT

To butt join steel bars and maintain any tightly abutting, or accurately spaced position of the bars to be joined, wires of high tensile strength (such as piano-type wires and the like) are located right next to the rod to be joined, the entire assembly then being surrounded by a tubular sleeve which is compressed and cold flowed over the wires and the rods to be joined together; compressive force can be reduced by forming spaced upstanding ridges on the sleeve, the compressive force being applied only against the ridges. The space bridging the ends of the rods to be joined is left free of compression ridges.

United States Patent 1191 Gutmann 14 1 Apr. 24, 1 973 BUTT JOINING OFSTEEL BARS AND CONNECTION ASSEMBLY THEREFOR [76] Inventor: SiegfriedGutmann, Schwarzwald- [63] Continuation-impart or Ser. No. 690,214, Feb.13,

I967, P31. No. 3,551,999.

[56] References Cited UNITED STATES PATENTS 2,490,809 Holke ..287/109650,860 6/1900 McTighe ..287/78 x 3,551,999 1/1971 Gutmann ..287/109FOREIGN PATENTS OR APPLICATIONS 1,044,465 9/1966 Great Britain ..24 123w Primary ExaminerAndrew V. Kundrat Attorney-Flynn & Frishauf [5 7]ABSTRACT To butt join steel bars and maintain any tightly abutting, oraccurately spaced position of the bars to be joined, wires of hightensile strength (such as piano-type wires and the like) are locatedright next to the rod to be joined, the entire assembly then beingsurrounded by a tubular sleeve which is compressed and cold flowed overthe wires and the rods to be joined together; compressive force can bereduced by forming spaced upstanding ridges on the sleeve, thecompressive force being applied only against the ridges. The spacebridging the ends of the rods to be joined is left free of compressionridges.

1 1 Claims, 5 Drawing Figures BUTT JOINING OF STEEL BARS AND CONNECTIONASSEMBLY THEREFOR CROSS REFERENCE U.S. application Ser. No. 690,214, ofwhich the present application is a continuation-in-part, filed Feb. 13,1967 and now US. Pat. No. 3,551,999, granted Jan. 5, 1971.

The present application, with respect to FIGS; 14 hereof, is acontinuation-in-part application of the prior application Serial 690,214and now Patent No. 3,551,999.

The present invention relates to a butt joint to splice steel rodstogether, and to a connection assembly to make the butt joint, and moreparticularly to a type of joint and connection assembly in which atubular sleeve of a material somewhat softer than the steel rods to bejoined is cold flowed thereover to non-removably and tightly join therods together.

Butt joints of steel rods, particularly when used to join together rodsto be embedded in cement to form reinforced concrete should be so joinedthat the total overall length of the two rods to be joined does notchange when the splice is made. The aforementioned application Ser. No.690,214 (now US. Pat. No. 3,551,999) discloses and claims a method,according to which the end pieces of the rods to be joined are tightlyheld against each other, so that the overall length will not change. Itmay happen, however, that the ends cannot, or should not be tightlyplaced against each other, due to the arrangement of the rodsthemselves, or to extend the length of both rods by a small, additionalamount. Avoiding changes in length of reinforcing rods which are to bespliced together is particularly important when partially pre-castreinforced cement blocks are to be joined together at exposed points ofthe rein-.

forcing rods.

It has been found in actual practice that merely enclosing reinforcingrods with a tubular sleeve, and coldworking the tubular sleeve by coldflowing the material over the reinforcing rods does not provide thedesired result, since, upon cold flowing the sleeve, a certain axialcomponent of pressure can be applied to the sleeve so that a gap willform between abutted ends of the sleeve,which gap will have anuncontrollable length. If the rods already are spaced by a slightamount, for example by being accurately pre-located, or have a spacerplaced therebetween, then the relative axial location of the ends of therods may still change by an uncontrollable amount.

It is an object of the present invention to form an end-to-end, or buttjoint of steel rods in which the overall length of the rods to be joinedwill not change, and to provide a connection assembly to make such ajoint.

SUBJECT MATTER OF THE PRESENT INVENTION tion theends of the tubularsleeve will cold flow over the ends of the wires, gripping in tightcontact the rods to be spliced as well as the wires themselves,

. The present invention is based on the realization that, upon coldflowing, the material of the sleeve deforms in longitudinal as well asin transverse direction; during the longitudinal deformation, the wiresinterposed betweenthe rods to be joined and the sleeve form, what may betermed a sliding surface or buffer zone for the cold flowing sleevematerial which, due to the presence of the wires, will not carry alongthe rods to be joined beneath the wires. Thus, the rods to be joinedbeneath the wires do not change their relative position in axialdirection. Additionally, the steel wires increase the tensile, as wellas compressive and bending strength of the joint without measurably orobjectionably increasing the axial dimension of the joint being formed.

In accordance with a feature of the invention, outer ribs, for examplecircumferential rings can be formed on the sleeve, compressive forcepressure being applied against these ribs. The zone between the ends ofthe rods to be spliced is free of ribs. It has been found that thepressure at the inner surface of the tubular sleeve increases uponapplication of pressure to the ribs only, without increased overallcompressive force being necessary to cold flow the sleeve materialitself.

The invention will be described by way of example with reference to theaccompanying drawings, wherein:

FIG. 1 is a longitudinal, partially sectional view of a joint inaccordance with the present invention;

FIG. 2 is a longitudinal cross-sectional view ofa connection assembly,the left side being shown before deformation and the right side afterdeformation; the rods to be joined have been omitted from this drawing;

FIG. 3 is a transverse cross-sectional view of the joint beforecompression;

FIG. 4 is a transverse cross-sectional view of the joint aftercompression; and

FIG. 5 is a longitudinal view, partly in section, of an additionalembodiment of the present invention.

The invention is being described with reference to joining reinforcingbars or rods, to be used with reinforced concrete. It is frequentlynecessary to join reinforcing bars or rods directly at a constructionsite and to manufacture a junction which has tensile, compressive,andbending strength commensurate with that of the un'-spliced rodsthemselves, without changing the overall dimension of two rods to bejoined, or keeping the overall length of the two rods to be joined,together with a small gap, at a constant and predetermined amount. Asillustrated in FIG. 1, a pairof rods 1, 2, to be joined, are surroundedby a tubular sleeve 3, of double-conical outer form, the major diameterof the cone being approximately in the region. of the ends of the rods1, 2, to be joined together. These rods may be butted tightly againsteach other, or can be spaced with a predetermined gap; or, a spacerelement to determine the amount of the gap can be placed between therods.

A plurality of small rod-like wires 4 are interposed between the rods 1,2 and tubular sleeve 3; they bridge the gap, if any, between rods 1, 2and have a length approximately equal to that of the sleeve 3, beforedeformation. They may be slightly shorter, of about the same size, orslightly longer. The number of these rods is just sufficient to coverthe outer surface of the reinforcing rods 1, 2, to be spliced together,or the inner surface of tubular sleeve 3 before deformation (see FIG.3). Upon application of a compressive force against the'circumference ofthe sleeve 3, as illustratedbytarrows A (FIG. 4), the material of thesleeve 3 will cold flow around the steel wires 4, which will be pressedagainst and follow the profile of the reinforcing bars 1, 2 (see FIGS.1, 4) and securely press the steel wires 4 against the reinforcing rods1, 2; simultaneously, these wires act as a sliding or slipping surfacefor the material of sleeve 3 which flows thereabout and preventsrelative change of position of the two reinforcing rods 1, 2, withrespect to each other, and more particularly an axial movement away fromeach other, that is tending to form a gap between the rods, or toincrease any pre-existing andv measured gap. When the sleeve 3 iscompletely cold flowed, the wires will prevent any additional change ofposition of the two rods 1, 2, with respect to each other due toexternal loading. The deformed wires, upon cold flowing of the sleeve,are tightly covered and embedded in the sleeve material which, itself,and through the entire length of the sleeve will penetrate any spacesbetween the wires themselves and tightly grip their surfaces. A suitablematerial for the wires 4 is a high tensile strength steel, for exampleof a strength of 200 kg/mm such material has been found suitable andincreases the strength of the junction considerably.

The compressive force, that is the die used to compress the tubularsleeve together preferably has an inner shape to provide for thedouble-conical form illustrated in FIG. 1.

FIG. 2 illustrates, in cross-sectional view, at the lefthand side asleeve 13 with inserted steel wires 14, before deformation. As seen, thesteel wires are slightly longer than the sleeve 13. Upon deformation, asseen on the right-hand side of FIG. 2, the ends of the sleeve 13 willflow over the steel wires 14, which have been deformed to assume theshape of any ridges, or grooves formed in the reinforcing bars (notshown and omitted from FIG. 2). The steel wires 14, themselves, did notchange in length. If rods are to be placed in butt end alignment intothe sleeve of FIG. 2, the two rods would butt against each other alongthe center line C. The steel wires can readily accept the outsidecontour of the rods 1, 2 to be spliced since their diameter is selectedto be small with respect to the diameter of the rods to be joined, asclearly appears from FIGS. 3 and 4.

A connection which has been found particularly suitable is illustratedin FIG. 5, in which a sleeve 23 is formed with projecting ribs 25,formed, preferably, as circumferential rings. Rods 21, 22 to be joinedare separated by a predetermined gap 26. The ribs 25 are separated fromeach other by rib-free zones 27; a central rib-free zone 28 is providedwhich bridges the gap 26 between the ends of the rods 21, 22 to bejoined, and the wires 24, inserted between sleeve 23 and rods 21, 22.Compressive force is applied by a pressure tool against the ribs 25, asschematically illustrated by arrows A (with respect to a few of the ribsonly, for simplicity of the drawing). The compressive force is.con-'centrated. As experiments have shown,'the total power" required toobtain a complete and tightjoint of rods 21, 22 by cold flowing thematerial of the sleeve 23 is substantially reduced and, additionally,the wires 24 are particularly well deformed to match the circumferenceof rods 21, The gap 26, bridged by the wires 24 is accuratelymaintained, so that the overall length of rods'2l, 22, and the gap 26willremain unchanged and the formation of the joint, including thesurrounding compression sleeve does not change any predetermined anddesired dimensions.

The compression of the sleeve, with the interposed wires 4 (FIG. 1), 14(FIG. 2) or 24 (FIG. 5) can be carried out in steps by first compressingone side, for example to the left of the central zone of the sleeve, andthen by compressing the sleeve at the other side of the central zone.Insertion of the wires 4, 14, 24 effectively prevents any change inrelative position of the inserted rods, even if compression is done instages.

I I claim:

1. Butt joint to splice rods located in end alignment with the endsbeing spaced by a gap (26) comprising a plurality of wires (4, 14, 24)of high tensile strength material placed adjacent said rods (1, 2, 21,22) to be spliced and bridging the gap (26) between the ends of saidrods, said wires extending beyond the gap and substantially parallel tosaid rods;

and a tubular sleeve (3, 13, 23) of deformable material extending oversaid wires and being compressed and cold flowed over said wires and saidrods to be spliced and tightly gripping said rods and said wires.

2. Joint according to claim 1, wherein said tubular sleeve is slightlydouble-conical, with the major diameter of the cone lying approximatelyover the region of the ends of said rods to be spliced together.

3. Joint according to claim 1, wherein said wires have their approximatemidpoint at the ends of said rods and beneath said sleeve and extendessentially in parallel to both said rods.

4. Joint according to claim 1, wherein said wires have a diameter smallwith respect to the diameter of the rods to be joined;

and a sufficient number of said wires are provided to essentiallytotally cover the circumference of said rods to be joined.

5. Joint according to claim 1, wherein said tubular sleeve has an outersurface, said outer surface being formed with projecting ribs overlyingsaid rods and leaving a rib-free zone (28) in the region of the sleevebridging the gap between the ends of said rods, said ribs (25) havingthe compressive force (A) applied thereto during cold flowing;

whereby, upon application of pressure to cold flow said sleeve againstthe rods, direct pressure will not be applied to the zone overlying theends of said rods tending to change the gap between the ends of saidrods during said cold flowing.

6. Joint according to claim 1, wherein said sleeve is cold flowed overthe ends of the wires and against the rods to be spliced together.

7. Connection assembly to form the connection of claim 1, saidconnection assembly comprising a tubular sleeve having a length which islarge with respect'to the gap between the rods and a plurality of hightensile strength wires'of a diameter small with respect to the innerdiameter of the sleeve and of similar length as the axial length of thesleeve'to bridge the gap between said rods and lie parallel to andalongside the rods beneath the sleeve, and of sufficient number toapproximately cover the inner surface of said sleeve.

8. Assembly according to claim 7, wherein said tubular sleeve is formedwith ring-like ribs (25) at its outer surface, said ribs lying on bothsides of a median zone (28) of said sleeve and adapted to overly theends of the rods to be joined together, so that the zone (28) overlyingthe ends of said rods will be free of ribs;

whereby, upon application of pressure to cold flow said sleeve, againstsaid ribs, direct pressure will not be applied to the zone overlying theends of said rods and tending to change the gap between the ends of saidrods during cold flowing.

9. Butt joint to splice rods located in end alignment comprising aplurality of wires (4, 14, 24) of high tensile strength material placedadjacent said rods 1, 2, 21, 22 to be spliced and bridging the ends ofsaid rods;

and a tubular sleeve (3) of deformable material extending over saidwires and being compressed and cold flowed over said wires and said rodsto be spliced, and tightly gripping both said rods and said wires, saidtubular sleeve being slightly double-conical with the major diameter ofthe cone lying approximately over the region of the ends of said rods tobe spliced together.

10. Joint according to claim 9, wherein said wires have theirapproximate midpoint at the ends of said rods and beneath said sleeveand extend essentially in parallel to each other.

11. Connection assembly to form the connection of claim 9, saidconnection assembly comprising a tubular sleeve of slightlydouble-conical form with the major diameter of the cone lyingapproximately over the region of the ends of the rods to be splicedtogether, and having a length which is large with respect to itsdiameter;

and a plurality of high tensile strength wires of a diameter small withrespect to the inner diameter of the sleeve and of similar length as theaxial length of the sleeve to bridge the ends of said rods and lieparallel to and alongside the rods beneath the sleeve, and of sufficientnumber to approximately cover the inner surface of said sleeve.

1. Butt joint to splice rods located in end alignment with the endsbeing spaced by a gap (26) comprising a plurality of wires (4, 14, 24)of high tensile strength material placed adjacent said rods (1, 2, 21,22) to be spliced and bridging the gap (26) between the ends of saidrods, said wires extending beyond the gap and substantially parallel tosaid rods; and a tubular sleeve (3, 13, 23) of deformable materialextending over said wires and being compressed and cold flowed over saidwires and said rods to be spliced and tightly gripping said rods andsaid wires.
 2. Joint according to claim 1, wherein said tubular sleeveis slightly double-conical, with the major diameter of the cone lyingapproximately over the region of the ends of said rods to be splicedtogether.
 3. Joint according to claim 1, wherein said wires have theirapproximate midpoint at the ends of said rods and beneath said sleeveand extend essentially in parallel to both said rods.
 4. Joint accordingto claim 1, wherein said wires have a diameter small with respect to thediameter of the rods to be joined; and a sufficient number of said wiresare provided to essentially totally cover the circumference of said rodsto be joined.
 5. Joint according to claim 1, wherein said tubular sleevehas an outer surface, said outer surface being formed with projectingribs overlying said rods and leaving a rib-free zone (28) in the regionof the sleeve bridging the gap between the ends of said rods, said ribs(25) having the compressive force (A'') applied thereto during coldflowing; whereby, upon application of pressure to cold flow said sleeveagainst the rods, direct pressure will not be applied to the zoneoverlying the ends of said rods tending to change the gap between theends of said rods during said cold flowing.
 6. Joint according to claim1, wherein said sleeve is cold flowed over the ends of the wires andagainst the rods to be spliced together.
 7. Connection assembly to formthe connection of claim 1, said connection assembly comprising a tubularsleeve having a length which is large with respect to the gap betweenthe rods and a plurality of high tensile strength wires of a diametersmall with respect to the inner diameter of the sleeve and of similarlength as the axial length of the sleeve to bridge the gap between saidrods and lie parallel to and alongside the rods beneath the sleeve, andof sufficient number to approximately cover the inner surface of saidsleeve.
 8. Assembly according to claim 7, wherein said tubular sleeve isformed with ring-like ribs (25) at its outer surface, said ribs lying onboth sides of a median zone (28) of said sleeve and adapted to overlythe ends of the rods to be joined together, so that the zone (28)overlying the ends of said rods will be free of ribs; whereby, uponapplication of pressure to cold flow said sleeve, against said ribs,direct pressure will not be applied to the zone overlying the ends ofsaid rods and tending to change the gap between the ends of said rodsduring cold flowing.
 9. Butt joint to splice rods located in endalignment comprising a plurality of wires (4, 14, 24) of high tensilestrength material placed adjacent said rods 1, 2, 21, 22 to be splicedand bridging the ends of said rods; and a tubular sleeve (3) ofdeformable material extending over said wires and being compressed andcold flowed over said wires and said rods to be spliced, and tightlygripping both said rods and said wires, said tubular sleeve beingslightly double-conical with the major diameter of the cone lyingapproximately over the region of the ends of said rods to be splicedtogether.
 10. Joint according to claim 9, wherein said wires have theirapproximate midpoint at the ends of said rods and beneath said sleeveand extend essentially in parallel to each other.
 11. Connectionassembly to form the connection of claim 9, said connection assemBlycomprising a tubular sleeve of slightly double-conical form with themajor diameter of the cone lying approximately over the region of theends of the rods to be spliced together, and having a length which islarge with respect to its diameter; and a plurality of high tensilestrength wires of a diameter small with respect to the inner diameter ofthe sleeve and of similar length as the axial length of the sleeve tobridge the ends of said rods and lie parallel to and alongside the rodsbeneath the sleeve, and of sufficient number to approximately cover theinner surface of said sleeve.